Proceedings of the Seminar on
United Nations for a Better World
Held on the Occasion of the
Fiftieth Anniversary of
United Nations
Sponsored by
Kengal Hanumanthaiya Foundation
Bangalore
June 26th - 28th 7995
SESSION-4: SCIENCE & TECHNOLOGY FOR HUMAN WELFARE
BIODIVERSITY = CHALLENGES AND
OPPORTUNITIES
Raghaveiidra Gadagkar
Centre for Ecological Sciences, IISc,
Bangalore- 12
and
Jawaharlal Nehru Centre for
Advanced Scientific Research,
Bangalore-64.
T h e most reliable guess of scientists
is that the universe, as we know it today,
began as a great explosion of truly
cosmic proportions about 25 billion
years ago. Before this explosion, all
matter of the universe is believed to have
existed as a highly condensed "cosmic
egg''. This explosion, some what
moderately termed the "big bang" is
expected to have sent the matter in the
"cosmic egg" flying out into the universe
to form countless numbers of stars.
Many such groups of stars constitute a
galaxy and galaxies are known to be
clustered into groups. Our own so-called
cluster of galaxies called the "local
group" consists of some 24 galaxies one
of which is the Milky way. The milky
way itself consists of over a hundred
billion stars one of which deserves
s p e d attention - this is what we call
the Sun. The sun, being one of tliese
billions of stars, has 9 planets revolving
a r o u n d it. The third s u c h planet,
counted by distance from the sun is the
earth, an approximately spherical body
with a diameter of 12,754 kms and a
surface area of over 510 million sq.kms.
AS far as we know our earth is the only
planet among the many hundreds of
billions that must be around, to possess
that remarkable entity called Life.
The earth was born about 4.6 billion
years ago and by complex chemical
reactions, a primitive form of life is
thought to have originated on earth
about 3.6 billion years ago. The living
entities, being capable of dividing and
changing, set off a chain of events we
now refer to as biological evolution. For
nearly 3 out of these 3.6 billion years,
life remained as microscopic blobs of
protoplasm in the ocean. But about 600
million years ago living organisms
became larger and more diverse and
came to possess hard skeletal structures
that leave behind impressions on rocks.
These so-called fossils permit us a
glimpse of the drama of life played on
earth during the past 600 million years
or so.
The major scenes in this drama were
the evolution of plants and animals that
could live on land instead of water about
400 million years ago, the arrival- of
,
insects and reptiles about 300 million
years ago, of birds and mammals about
200 million years ago and flowering
plants about 150 million years ago
(Figure 1). This gradual and relatively
smooth evolution of progressively more
complex forms of life received a major
jolt about 2 million years ago with the
origin of a rather special lineage of
primates referred to as the genus Homo.
About 40,000 years ago a single species
of this line called Homo sapiens had
arrived on earth with all the qualities of ’
modem man as we know him today.
Perhaps the most distinctive qualities of
Homo s~pienswere their intelligence and
t h e i r ability to manipulate their
environment. These qualities permitted
Homo sapiens to gain unprecedented
mastery over their environment. The
most important element of their mastery
w a s t h e ability to control a n d
manipulate other forms of life. Quite
naturally Homo sapiens perfected the art
of cultivating species of plants and
animals that were useful to them agriculture and animal husbandry are
modern terms that describe these arts.
Never before had one form of life gained
such mastery over its physical and
biological environments. Not only did
Homo sapiens control other forms of life
but it also manipulated its physical
environment to such an extent that for
the first time a species of living organism
c u t loose from t h e constraints of
biological evolution and produced five
billion individuals. The same qualities of
Homo sapiens t h a t permitted space
exploration and a visit to the moon also
permit u s to reflect on our past, present
and future. This ability to reflect is
perhaps o u r greatest saviour. The
euphoria associated with mastery of the
universe, with the ability to increase our
own life expectancy, to genetically
engineer other forms of life, to sequence
the human genome, to contemplate
setting up colonies of human being on
other planets, unfortunately led u s to
neglect the state of our own planet - a
state caused by our own activities.
In the last 25 years or so however,
there h a s beem a r a t h e r s u d d e n
realization that we have damaged our
planet beyond recognition and perhaps
beyond repair. We have destroyed its
life-support systems that had evolved
before us over billion of years. We have
burnt fossil fuels and cut down forests
on s u c h a large scale that the
temperature of the earth has increased
perceptibly. The planet earth cannot
support our efforts to grow food, provide
shelter, not to speak of consumer goods,
to a human population that is growing
in numbers and in its demands at the
present rate. This chilling realization has
perhaps begun to dawn on a reasonable
number of us today. An even more
chilling realization is however on its way.
Not many of us realize that we are
destroying, perhaps by the dozens every
day, our fellow living creatures that have
evolved like u s over billions of years.
Man’s activity on earth is rendering
extinct these magnificent forms of life at
a rate never before seen. This wealth of
life is known by the term that has
recently become fashionable biodiversity. Biodiversity is on its way to
becoming a house-hold word and has
already entered the vocabulary of our
politicians and administrators. But few of
us realize that even scientists know very
little about this biodiversity that we
would now like to save.
What is this biodiversity after all. We
do know a few things about biodiversity.
We know that biodiversity is spectacular.
The earth abounds in myriad forms of
living organisms. Today it is customary
to recogniscb five- kingcloiiis of living
organisms: (1) Protista (that consists of
011 earth - our own fellow creatures with
bacteria a n d blue-green algae), (2)
whom we share our entire past? m e n
Monera (that consists of advanced
ignoring the fact that many species are
algae), (3) Fungi. (4) Plants and (5) going extinct every day, it is not an easy
A.nimals. Living organisms are found
task to record, describe or even count
almost every where - the deep sea, ~ l e the number of species. Life forms are so
diverse that many years of specialized
polar caps, the hot springs, not to
training is required to be able to
mention the tropical rain forests. They
recognize and describe them. Even such
range in size fi-om viruses which may be
training drill render one literate oiily in
not more than a millionth of a meter in
the realm of one small group of living
She t0 the African elephant that weighs
organisms. Small numbers of scientists,
6.5 tones and stands over three meters
often unheard of and unsung have been
tall. the blue whale which may be over
painstakingly naming and describing
30 meters long or the red wood tree that
living organisms for about 200 years.
is over as 100 meters tall. They may
Indian tcwonomists have so far named
swim in water, fly in the air, crawl on
and described some eighty t h r e e
land or burrow under the soil, They may
thousand species (Figure 4) while
reproduce once every 20 minutes as
taxonomists t h e world over have
some bacteria are capable of doing or
described about 1.8 million species
once in 20 years as some mammals do.
(Figure 5).From these numbers the total
One especially surprising fact about
number of species of living organisms
biodiversity
is
its
apparent
was being estimated, until recently, a t
"lopsidedness". An overwhelming
about 5-10 million. Then came a major
proportion of the animal biomass in
jolt. Scientists from the Smithsonian
tropical forests is contributed by insects
Institution, especially T.L. Erwin realized
(Figure 2) and among the insects by
that most insects studied so far were
social insects such as ants and termites
from the forest floor. The forest canopy
was essentially unexplored. This last
(Figure 3). In a Brazilian tropical forest
biotic frontier, the tropical forest canopy
for example, it has been estimated that
has now been carefully explored by
the biomass of ants is approximately 4
using a new and more powerful method.
times that of all vertebrates (i.e..
This
involves killing all insects and other
a m p h i b i a n s , reptiles, birds and
forms of life inhabiting selected trees by
mammals) p u t together. Few of u s
covering t h e trees with a fog of
realize the "insignificant" role of higher
insecticide. To everyone's surprise
animals such as vertebrates compared
hundreds of species of insects entirely
to ants and other insects in tropical
new to science were discovered dn the
forest ecosystems.
canopies of j u s t a few trees in Panama.
All this is fine but pray - how nlanY Such richness and newness of tropical
Mnds of living organism are there on
forest canopy arthropod fauna has been
earth? Unfortunately that's asking to0
confirmed by other scientists such as
much, Seems a bit embarrassing does it
Nigel Stork of the British Museum of
not - we. know about distant galaxies
Katural History using similar methods
and have a reasonable guess of the
in Borneo. All t h i s suggests t h e
number of stars in the universe but
possibility that the number of species of
cannot ever guess the number of species
insects on earth is really much larger
than supposed earlier. One estimate
puts the expected number at 30 million
for arthropods alone Fable I f . Thus our
estimate of the number o$ species of
living organisms on earth varies from 5
million to over 30 million - not a very
precise estimate indeed.
painstaKing work by highly trained
biologists. More difficult, it will require
foresight and imagination on the part of
science a d m i n i s t r a t o r s a n d the
realization t h a t t h i s a worthwhile
exercise, deserving of all our support,
financial and otherwise.
Conserving biodiversity is perhaps our
most challenging t a s k ahead. As
Harvard University biologist Edward 0.
Wilson has said. ‘The worst thing that
can happen - will happen - is not energy
depletion. economic collapse, limited
nuclear war, or conquest by a
totalitariaii government. As terrible as
these catastrophes would be for us, they
c a n be repaired within a few
generations. The one process ongoing,
that will take millions of years to correct
is the loss of species diversity by the
destructjon of natural habitats. This is
the folly our descendants are least likely
to forgive us.” But we can hardly expect
the political will, the hard work and the
social participaeon needed to conserve
biodiversity if there doesn’t exist even a
reasonable catalogue of biodiversity, let
alone documented uses of different
species. But estimating biodiversity is
perhaps an even greater challenge. I t will
r e q u i r e millions of m a n days of
Clearly we need an urgent debate
among scientists as well as policy
makers about the significance of the
findings that insects constitute such an
overwhelming proportion of animal
biomass and animd species and even
more about the possibility that the total
number of species of life forms may be
of the order of 30 million. How should
educated, enlightened citizens of the
world respond to these rather shocking
fiiidings? Should we r e a d j u s t o u r
priorities. Is there any point at all in
t ~ o n o m i continuing
s~
to describe new
species at the present slow rate? Should
we forget about 30 million arthropod
species and let them go extinct. Or
should we catalogue, describe and try to
conserve as many of them as possible.
What are the investments in time, effort
and money that will be needed. How can
we compute costs and benefits of our
decisions in these matters? At the very
least we need an informed debate.
TABLE I
ARTHROPOD SPECIES DIVERSITY
-
THE LOGIC OF THE 30 MILLION ESTIMATE
1.
Number of beetle species fogged from 19
L. Seemanniitrees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.
Average host-specificity for beetles is 13.5% - therefore
number of beetle species host-specific to L. seemannii.
3.
4.
5.
1
................
Number of tropical tree species is about 50,000 - therefore
number of beetle species host-specific to these . . . . . . . . . . . . . . . . . . . . . . .
Beetles represent 40% of canopy arthropod species,
therefore number of species of tropical canopy arthropods
1,200
163
8,150,000
..............
20,000,000
Canopy is twice as rich as the ground in species of arthropods,
therefore total number of tropical rain forest arthropods. . . . . . . . . . . . . . . . .
30,000,000
[Modified from Stork (1988). Data from Erwin (1982)]
Evolution Of Life On Earth
PALEOZOIC
gqEm
Millions of
years ago
cv
Conifers
Cycads
Ferns
Club mosses
Horse tails
Mosses
Bacteria, Algae,
Lichens 8
Fungi
Single celled animals
Sponges
II Jellyfish & Corals
.’
F I al wor m s
Brachiopods
I
Single - shelled
molluscs
Bivalve molluscs
Squid & OCfOPlJS
Segmenled worms
Spiders & Scorpions
Crustaceans
Centipedes &
Millipedes
Insects
Echinoderms
I
--
I
I
I
Fish
A mphiblans
Re pliles
Birds
Mammals
Total Animal Biomass
Ants &
(Data from Fittkau and Klinge 1973)
Figure 2
. . .
,
. . ..
"
Insect Biomass
Orthoptera
Others
Lepidoptera
Coleoptera
\
\
(Data from Fittkau and Klinge 1973)
Figure 3
/
SociaWasps
A
1
m
Q)
.
d
0
Q)
a
m
w
Described World Species
lowering plants - 250000 (13.6%)
Other Arthropods
Other Invertebrates
200000 (1 0.9%)
-
Non flowering plants - 130000 (7.1%)
-
Mammals - 4170 $2%)
Birds 9018 (0.5%)
Reptiles - 5084 (0.3%)
Amphibians - 3300 (0.2%)
Fishes - 4100 (2.2%)
-
Insect - 1000000 (54.3%)
Data supplied by Marc Collins
Figure 5